A liquid crystal display element utilizes the changes of optical properties for displaying, such that the change is made by outside stimulus such as electric fields to change the alignment state of liquid crystal molecules. Such a liquid crystal display element has a structure in which liquid crystal molecules are filled in the gap between two pieces of transparent substrates, and generally, an alignment treatment is applied to the inside of substrates where the liquid crystal molecules contact, in order to align the liquid crystal molecules in a predetermined direction.
The alignment treatment can be roughly classified into two: One is a rubbing method by forming a polymer film such as polyimide on the substrate surface such as glass, which is then rubbed by cloth or the like; and the other is a light alignment method by irradiating light having anisotropy onto the coating film provided on the substrate to provide a liquid crystal alignment ability. The former method, i.e., the rubbing method, is advantageous since the rubbed direction becomes parallel to the longitudinal axis (director) direction of the liquid crystal molecules contacting the substrate, and the production device of the alignment film is simple. However, there have caused problems such as orientation defects occurred due to scratches or dusts on the orientation film surface during the manufacturing process. In addition, as the size of the substrate is upscaled, it has become more difficult to design and maintain a rubbing device to obtain uniform orientation over the entire surface of the substrate and for a long period of time.
On the other hand, the latter method, i.e., the light orientation method is characterized in that a light is irradiated to a compound having a group whose absorbency of the light varies depending on the direction of the electric vector of a polarized light polarization (which is hereinafter referred to as a light orientation group) so as to align the light orientation group into a certain direction, thereby providing a liquid crystal molecule contacting the light orientation group with a liquid crystal orientation ability. Therefore, this method can solve the problems of the rubbing method, such as the orientation defects caused due to the scratches or dusts, or problems in obtaining uniform orientation over the entire surface of the substrate and for a long period of time.
However, in the light orientation method, a significant amount of light exposure dose is required to obtain a practical level of the liquid crystal orientation ability. In particular, when obtaining a large area of a light orientation film, a high power ultraviolet ray lamp is required to be irradiated for a long period of time. As a technique to reduce the light exposure dose, Patent Reference No. 1 discloses a manufacturing method of a liquid crystal alignment film in which a molecule of the compound in the coating film is oriented in a direction corresponding to the polarized light direction by irradiating polarization ultraviolet rays on the coating surface, followed by burning the coating film.
Also, when irradiating with a high power ultraviolet rays lamp for a long time, there causes a problem that the compound having the light orientation group causes photolysis at an irradiated area so as to deteriorate its liquid crystal orientation ability. For example, Patent Reference No. 2 discloses a method in which a part of a photosensitive thin film is irradiated with first radiation exposure, and then, the entire surface of the thin film is irradiated with second radiation exposure that is different from the first radiation exposure in at least one of the polarization state of radiation, the direction of the optical axis, and the energy.